Alternatively you can choose the "Secure mode" to run the VGA option rom in a contained environment.

If you have no on-board graphics, you are done configuring coreboot at this point. You may exit configuration, and run make to get your VGA enabled coreboot image.

On-board Video Devices

If you run coreboot on a system with on-board graphics, you have to embed a VGA on the top level, enter the file name of your option rom and the PCI ID of the associated graphics device in the form <vendor_id>,<device_id>:

Downloading

There are sites that have video bios roms on their website. (I know of this one for nvidia cards: [1])

For Intel onboard graphics you can download the vbios(vga bios) from Intel's download section. The vbios is included with some versions of the graphics driver. The summary will say something like "NOTE:These materials are intended for use by developers.Includes VBIOS". The actual vbios file is the *.dat file included with the graphics driver.

Extracting from the system (if everything else fails)

However you might be able to retrieve your on-board video bios with Linux as well.

Boot up a machine with a commercial bios (not coreboot) with the video card you wish to work under coreboot.

You can see where and how much your card's bios is using by doing a

cat/proc/iomem |grep'Video ROM'

From the command line enter:

ddif=/dev/mem of=vgabios.bin bs=1k count=64skip=768

This assumes you card's bios is cached at 0xc0000, and is 64K long.

ddif=/dev/mem of=video.bios.bin.4 bs=65536count=1skip=12

This works for many of the VIA Epia boards.
Alternatively you can automatically generate it using this nice script from Peter Stuge: